The present invention relates to a false twist unit or device, in particular for false twist spinning, comprising a suction portion containing a converging suction channel or passage and a throttle location or position following thereat, considered with respect to a predetermined direction of yarn or thread movement, and with a twist imparting means following the suction portion.
A false twist unit or device of the above mentioned type is known from Swiss Pat. No. 617,465. With this false twist unit fibers delivered from a drafting mechanism are spun to a yarn or thread or the like. The twist imparting means comprises a pneumatic false twist nozzle by means of which, on the one hand, twist is imparted to the yarn or thread and, on the other hand, air is drawn by suction through the suction channel or passage.
The disadvantage of this prior art arrangement is that the quantity of air drawn through the throttle location or position is insufficient to produce in the suction channel or passage an air speed or velocity which is optimal for the spinning process. The speed or velocity of the air which is required in order to draw in edge or marginal fibers, which in this spinning process are wound around the yarn core, should advantageously be at least greater than the speed of forward movement or advance of the yarn core.
Furthermore, from Swiss Pat. No. 572,113, a device for false twist spinning is known in which a suction portion, arranged before a twisting imparting means as viewed in the direction of travel of the thread or yarn, is provided with a suction channel or passage and a suction tube of approximately equal diameter arranged at right angles thereto.
The disadvantage of this prior art device is that, when a sufficient quantity of air is drawn in by suction, as a result of the considerable diversion of the air stream out of the yarn or thread path, the suction action must be interrupted for starting spinning which makes such so-called start spinning operation correspondingly difficult.
The expression "start spinning" or the like refers to the required guiding of the untwisted fiber sliver delivered by the exit or delivery roller pair into the twist imparting means during the starting-up procedure or operation.